Question

Short/long answer type questions:
Describe the fluid mosaic model of membrane structure as well as the model that preceded it. Cite the evidence that either disproves or supports these models.

Answer 1

Hint: The fluid mosaic model was a widely accepted model and was able to solve many of the questions related to cell structure. It was given by singer and Nicholson in 1972. Before him many scientists have given some of the model but it was unable to define why some molecule does not pass through the membrane.

Complete answer:
The Fluid Mosaic model was given by S.J.Singer and G.L.,Nicholson in 1972 which proves that plasma membrane is a mosaic model made up of phospholipids, cholesterol, proteins and carbohydrates. It's thickness ranges from 5-10 nm and it is 8 micrometre wide. It consists of dual phospholipids molecules. The hydrophilic part of the plasma membrane helps to enter the aqueous molecules and repel the lipid molecule while the hydrophilic part helps to enter the lipid molecule and repel water molecules. The arrangement of overall membrane is described as head and tail. Head part is made up of phosphate groups with polar character while the tail consists of nonpolar group glycerol. The integral part is made up of protein with 20-25 amino acids. Carbohydrates are present on the exterior part and show bounding with protein and lipids with presence of 2-60 polysaccharide units.
Before fluid mosaic model many scientists have described the structure of plasma membranes of cells but all that discovery is not able to prove why cell membranes allow only specific substances to enter and not all and only fluid mosaic model has proved that therefore fluid mosaic models are widely accepted models.

Note:
At low temperature the movement of cells is restricted due to less fluidity of cholesterol. The fluidity and elasticity of cells also get affected by the length of fatty acids, the greater the length of fatty acid the more its fluidity will be.